1. Field of the Invention
This invention relates to a stabilized cannula adapted to seal against the loss of gas pressure from a body cavity of a patient during a surgical procedure.
2. Description of the Prior Art
The insertion of a cannula into an abdominal cavity during laparoscopic surgery is generally accomplished using one of two methods. In the first method, a hollow needle is inserted into the body cavity prior to the insertion of the cannula so that the cavity can be expanded with a gas, such as carbon dioxide. Thereafter, the cannula is inserted along with a removable sharp obtruator. The obtruator blade cuts through the abdominal wall allowing the surrounding cannula to penetrate into the interior of the cavity. The obtruator is then removed leaving an entry port for various laparoscopic tools to be inserted into the cavity. The cannula is equipped with a seal at its proximal end to ensure that the cavity remains pressurized with the insertion and removal of various instruments. Pressure loss between the cannula and the cavity wall is reduced by the tightness of the fit between the cannula and the cavity wall because the outside diameter of the cannula is larger than the obtruator entry wound. Generally, the obtruator used in this method is equipped with a spring-activated shield that is designed to cover the blade as soon as the interior wall is penetrated to avoid inadvertent puncturing of the organs present inside the cavity. These shields sometimes fail to close quickly enough to avoid injuries, particularly if an organ such as the bowel is attached to the cavity wall.
A known method that avoids injuries associated with the obtruator shield involves direct incision of the wall by the surgeon. Using a small scalpel, the surgeon makes an incision through the cavity wall into the abdominal cavity and inserts a finger into the cavity to feel for organs that might be attached to, or near the abdominal wall. Upon a determination that no organs are attached to the abdominal wall, a cannula with an obtruator having a blunt tip is inserted through the cut. After placement of the cannula, the obtruator is removed. The purpose of the blunt tip of the obtruator is to guide the cannula through the cut down to wound.
Both of the above described methods of insertion are prone to gas leakage and the lack of a proximal-to-distal stability of the cannula. Various techniques have been attempted to minimize these problems. Known anchors for use with laparoscopic cannula have employed threaded sleeves adapted to be secured to the cannula and screwed into a laparoscopic puncture opening to secure the instrument in place. An anchor of this type is found in U.S. Pat. No. 5,217,441. U.S. Pat. No. 5,002,557 to Hasson discloses an inflatable balloon that seals the cannula against the inside wall of the cavity and stabilizes the cannula by employing a tapered collar that cinches against the outside wall of the cavity, in effect sandwiching the cavity wall between the collar and the inflated balloon. The Hasson device provides a sufficient seal and adequate cannula stability, but is difficult to operate. The balloon must be inflated with an external hypodermic syringe or other means through a stop cock. Additionally, sealing the cannula with the cavity wall involves three steps: inflating the balloon, pushing a tapered collar snugly against the external surface of the cavity wall, and securing the collar in place with a set screw. U.S. Pat. No. 5,697,946 to Hopper et al. discloses a balloon-anchoring device that does not require the use of a proximal collar, but instead relies on a portion of the inflating surface to come in contact with the entry wound, thereby wedging the cannula into position. The Hopper device also involves an external inflation device such as a hypodermic syringe connected to the cannula by a stop cock or check valve.
U.S. Pat. No. 5,330,497 to Freitas et al. describes an anchored cannula that uses an expandable mushroom-shaped anchor that in one embodiment opens when the user turns a detented actuator. The anchor cinches-up against the peritoneum when a seal is forced distally. The Freitas device offers an improvement over threads, but still suffers from several drawbacks. In particular, the Freitas device is unduly complex at least in that it requires multiple steps in order to expand the anchor and seal the external cavity wall. A multiplicity of steps during a surgical procedure can lead to a serious inefficiency. Devices that are simple to operate make the procedure more efficient and lead to less errors. Therefore what is needed is a simple, easy-to-use cannula anchoring and sealing device and method for use in laparoscopic surgery.